This invention relates to a fuel delivery rail assembly for an internal combustion engine, especially for an automotive engine, equipped with a fuel injection system. The fuel delivery rail assembly delivers pressurized fuel supplied from a fuel pump toward intake passages or chambers via associated fuel injectors. The assembly is used to simplify installation of the fuel injectors and the fuel supply passages on the engine.
There are two types of fuel delivery rail assemblies. One is a so-called top feed type and the other is a bottom flow type.
Japanese utility model public disclosure No. 152073/1987 discloses a typical design of the bottom flow type assembly, in which three tubular sockets are interconnected by connecting pipes. Each of the sockets is located at a predetermined distance from each other. These sockets are initially made through a forging process, and then directed to a precise machining operation. In this step, especially an interior surface of the socket should be smoothly, finished in order to establish a fluid tight seal with an O-ring. For this purpose, a special machining process utilizing burnishing work is commonly performed to effect a high grade of circumferential accuracy as well as surface smoothness.
Each socket comprises a tubular body having a top opening, a bottom opening and two lateral openings facing opposite directions. These lateral openings are used to receive distal ends of the connecting pipes. By means of brazing connections, the sockets and the pipes are fixed together.
Since the conventional fuel delivery rail assembly is constructed as stated above, many manufacturing steps are required for assembly. In particular, the brazing connections give rise to manufacturing difficulties. During a brazing operation, thermal distortion cannot be perfectly eliminated. As a result, there remain several drawbacks, such as fuel leakage and breakdown from the parting lines.
In U.S. Pat. No. 4,457,280 (Hudson), there is disclosed a top feed type assembly, in which the beam portion of the rail is split into two units, an upper portion and a lower portion. The sockets are brazed to one of the units. The units are combined together in a brazing operation. However, in this design, there is a disadvantage that the assembly tends to be bent or curved due to a thermal distortion caused by the brazing. The metallic material suffers from degradation and breakdown.
In Japanese utility model public disclosure No. 84362/1982, there is disclosed a die casting type assembly in which the sockets and the conduit are integrally formed through a die casting process. However, there are many problems such as inferiority of plating, increase and weight, or inside defects which are not visible from outside.